DESCRIPTION: With the discovery that many cDNA copies of picornaviral RNA genomes result in the synthesis of infectious virus after transfection into mammalian cells, picornaviruses became amenable to genetic manipulations. Because picornaviruses interact extensively with host macromolecular pathways, these viruses have been used as tools to study the mechanisms of host cell translation, transcription and protein secretion. The overall aim of this proposal is to study specific viral-host interactions that occur in infected cells, with the ultimate goal to understand picornavirus-induced pathogenesis. The first aim examines a functional role of the specific interaction of nucleolin with the viral 3' noncoding region. Specifically, the outcome of the relocalization of nucleolin from the nucleolus to the cytoplasm on viral gene expression will be studied in cell-free extracts that mimic many aspects of the infectious cycle. In addition, a virus-encoded function that induces the relocalization of nucleolin will be sought by monitoring the intracellular localization of nucleolin in the presence of individual viral polypeptides. Various forms of the translation initiation factor eIF4G have been implicated to be important in translation initiation by both the conventional 5' end-dependent scanning mechanism and the internal inititation mechanism. In the second aim, the roles of various forms of eIF4G in host cell translation and the poliovirus infectious cycle will be studied in cells in which the normal eIF4G gene is inactivated. In the last aim, genes will be identified that confer susceptibility to picornavirus infections. Random host genes will be disrupted by retroviral insertions and inactivated by expression of antisense RNA. Cells that have functionally inactivated allelic loci and that are resistant to infection by either picornavirus or rhinovirus will be selected and the disrupted genes will be identified and characterized in detail.